Network elements in various communication networks are required to measure the traversal latency of traffic through each network switch or router. The latency information gathered can be used, for example, in managing and optimizing the network performance.
Methods for measuring the traversal latency in a network element are known in the art. For example, U.S. Pat. No. 7,483,442, whose disclosure is incorporated herein by reference, describes an Infiniband switch that can have an input port logic unit for determining an output virtual lane for a received packet and for storing a descriptor of the determined output virtual lane in a packet field not protected by a checksum field of the packet. The switch can also have a routing unit for transferring the received packet to an output port corresponding to the determined output virtual lane. Additionally, the switch can have an output port logic unit for simultaneously checking the integrity of the packet transferred through the routing unit and calculating a new value for the checksum with the descriptor moved to a correct packet field, which field is included in the calculation of the checksum.